1. Field of the Invention
The present invention relates to a diversity receiving device that selects at least one received signal from a plurality of systems.
2. Description of the Related Art
In the mobile communication, a diversity receiving method that synthesizes received signals of a plurality of antennas or demodulation signals of a plurality of systems is adopted in order to improve the degradation of received signals due to multipath fading. In particular, in a diversity receiving method that synthesizes demodulation signals of a plurality of independent systems, enhancement of reception sensitivity is achieved to the maximum.
FIG. 14 is a block diagram showing the configuration of a known diversity receiving device. Here, two systems are exemplified as a plurality of systems. In FIG. 14, signals S100 and S101 received by antennas 200 and 201 are input to receivers 202 and 203, respectively, such that baseband received signals S102 and S103 are output. The received signals S102 and S103 are input to AFC and synchronizing units 206 and 207, respectively. Received signals S104 and S105 subjected to an AFC (Auto Frequency Control) processing and a symbol synchronization processing in the AFC and synchronizing units 206 and 207 are respectively input to modulating units 208 and 209. The received signals S102 and S103 are respectively input to received signal intensity detecting units 204 and 205, and reception intensity detection signals S109 and S110 output from the received signal intensity detecting units 204 and 205 are respectively input to a comparing unit 211. The demodulation signals S106 and S107 demodulated by the demodulating units 208 and 209 and the output of the comparing unit 211 are input to a synthesizing unit 211. The synthesizing unit 211 outputs a synthesize signal S108 subjected to a synthesis processing according to the output of the comparing unit 211.
With the above-described configuration, when there is a difference in line quality between the plurality of systems, demodulation signals can be synthesized according to the line quality of each system. However, when there is a system in which reception sensitivity is lowered due to fading, such that a signal-to-noise power ratio is degraded, stability of an AFC circuit operation of the system can be lowered, and a diversity gain can be degraded. JP-A-7-38478 discloses a technique that solves the problems using signals of a plurality of systems in common.
In the configuration of the known diversity receiving device, the receiving units 202 and 203, the AFC and synchronizing units 206 and 207, and the demodulating units 208 and 209 independently operates in each system. As a result, although enhancement of reception performance is achieved, power consumption increases because an unselected systems also operate at all times. Further, when there is a system in which reception sensitivity is lowered due to fading, such that a signal-to-noise power ratio is degraded, a more effective measure for enhancing reception performance is desired in order to prevent a diversity gain from being degraded.
An object of the invention is to provide a diversity receiving device that can reduce overall power consumption without degrading reception performance. Another object of the invention is to provide a diversity receiving device that can effectively prevent degradation of a diversity gain when there is a difference in line quality between systems.
According to an aspect of the invention, there is provided a diversity receiving device that selects at least one received signal from a plurality of systems. The diversity receiving device includes a unit that interrupts a power supply to systems other than a selected system. With this configuration, since the power supply to systems other than a selected system is interrupted, it is possible to reduce overall power consumption without degrading reception performance. Specifically, the diversity receiving device may include a plurality of receiving units that respectively receive signals coming into a plurality of antennas, a plurality of AFC and synchronizing units that respectively process the output signals of the receiving units through an AFC processing and a synchronization processing, a plurality of demodulating units that respectively demodulate the output signals of the AFC and synchronizing units so as to output demodulation signals, a plurality of line quality detecting units that respectively detect the intensities of the output signals of the receiving units so as to output reception intensity detection signals, a control unit that determines any one of a selection synthesis diversity for selecting one system and an addition synthesis diversity for selecting a plurality of systems and adding demodulation signals on the basis of a predetermined judgment criteria according to the reception intensity detection signals as a synthesis pattern of the demodulation signals, and outputs clock interruption control signals respectively interrupting the power supply to unselected systems and synthesis pattern selection signals respectively designating a synthesis pattern of demodulation signals of selected systems, a plurality of clock supply units that interrupt a clock supply to the AFC and synchronizing units and the demodulating units of the unselected systems according to the clock interruption control signals, and a synthesizing unit that synthesizes demodulation signals of the selected systems according to the synthesis pattern selection signals.
The diversity receiving device according to the aspect of the invention may further include a unit that synthesizes received signals of the respective systems through a time division processing. With this configuration, the received signals of the respective systems are synthesized through the time division processing, and thus it is possible to reduce the size of a circuit. Specifically, the diversity receiving device may include a plurality of receiving units that respectively receive signals coming into a plurality of antennas, a plurality of AFC and synchronizing units that respectively process the output signals of the receiving units through an AFC processing and a synchronization processing in a time-division manner, a plurality of demodulating units that respectively demodulate the output signals of the AFC and synchronizing units in a time-division manner so as to output the demodulation signals, a plurality of reception intensity detecting units that respectively detect the intensities of the output signals of the receiving units so as to output reception intensity detection signals, a control unit that determines any one of a selection synthesis diversity for selecting one system and an addition synthesis diversity for selecting a plurality of systems and adding demodulation signals on the basis of a predetermined judgment criteria according to the reception intensity detection signals as a synthesis pattern of demodulation signals, performs a control such that unselected systems are not subjected to the time division processing, and outputs clock period control signals designating a clock period of the time division processing according to the number of selected systems and synthesis pattern selection signals designating a synthesis pattern of the demodulated signals of the selected systems, a clock supply unit that supplies a clock of the period designated by the clock period control signal to the AFC and synchronizing units and the demodulating units, and a synthesizing unit that synthesizes demodulation signals of the selected systems according to the synthesis pattern selection signals.
The diversity receiving device according to the aspect of the invention may further include a unit that sends a signal received by an antenna in each system to other systems. With this configuration, a received signal can be sent to an arbitrary system, and thus it is possible to previously determine a system that guides a received signal required for diversity. Accordingly, the power supply to all circuit blocks, excluding the selected systems, can be interrupted. In addition, as the power supply to a receiving circuit that converts a high frequency into a baseband signal is interrupted, it is possible to further reduce power consumption. In general, power consumption of the high frequency may be significant. The diversity receiving device according to the aspect of the invention may include an antenna switching unit that selects one of signals coming into a plurality of antennas so as to output the signal to the receiving unit of the first system. When the selection synthesis diversity is determined as a synthesis pattern of demodulation signals, the control unit requests the antenna switching unit to select a signal coming into the antenna of the system selected on the basis of the judgment criteria. Further, the control unit performs a control such that the first system is set as the selected system and other systems are set as unselected systems, regardless of the judgment criteria, and the clock supply units of the unselected systems interrupt the clock supply to the receiving units of the corresponding systems. When the addition synthesis diversity is determined as a synthesis pattern of demodulation signals, the control unit requests the antenna switching unit to select a signal coming into the antenna of the first system.
The diversity receiving device according to the aspect of the invention may further include a unit that selects a selection synthesis diversity for selecting a received signal with the largest intensity or an addition synthesis diversity for adding all the selected received signals according to the intensity of a received signal. With this configuration, the selection synthesis diversity and the addition synthesis diversity can be switched dynamically according to the intensity of the received signal, and the synthesis pattern is not fixed. Therefore, even though there is a difference in line quality between the systems, it is possible to effectively prevent the degradation of the diversity gain.
The diversity receiving device according to the aspect of the invention may further include a unit that selects the selection synthesis diversity or the addition synthesis diversity according to a difference between a received signal with the largest intensity and a received signal with the second-largest intensity. With this configuration, since the selection synthesis diversity or the addition synthesis diversity is selected in consideration of the difference between the received signal with the greatest intensity and the received signal with the second-greatest intensity, it is possible to effectively prevent the degradation of the diversity gain. In the diversity receiving device according to the aspect of the invention, the predetermined judgment criteria for determining the synthesis pattern of demodulation signals is set to the selection synthesis diversity or the addition synthesis diversity. When the plurality of reception intensity detection signals are equal to or more than a predetermined first threshold value, or when only one of the reception intensity detection signals is equal to or more than the first threshold value and a difference from the reception intensity detection signal having the second-greatest intensity is equal to or more than a second threshold value, the judgment criteria is set to the selection synthesis diversity for selecting the system having the reception intensity detection signal is the greatest. When only one of the reception intensity detection signals is equal to or more than the first threshold value and a difference from the reception intensity detection signal having the second-greatest intensity does not reach the second threshold value, or when any one of the reception intensity detection signals does not reach the first threshold value, the judgment criteria is set to the addition synthesis diversity in which all the systems are selected and the demodulation signals are added.
The diversity receiving device according to the aspect of the invention may further include a unit that selects a received signal of a system in which a difference between a correlation value of received signals and average power of received signals is the largest. With this configuration, since a system having a large difference between the correlation value of received signals and the average power of received signals is selected, it is possible to select a system in which signal distortion is small and a preamble is ideal. In the diversity receiving device, the AFC and synchronizing unit outputs a difference between a correlation detection signal and average power in a corresponding system upon the AFC processing and the synchronization processing. When the plurality of reception intensity detection signals are equal to or more than the first threshold value, a predetermined judgment criterion for determining the synthesis pattern of demodulation signals is set to the selection synthesis diversity for selecting a system in which the difference between the correlation detection signal and the average power is large, instead of a system in which the reception intensity detection signal is the largest.
The diversity receiving device according to the aspect of the invention may further include a unit that selects the selection synthesis diversity or the addition synthesis diversity on the basis of a modulation method of a synthesized received signal. With this configuration, it is possible to select a synthesis pattern according to a modulation method of a received signal. For example, in a multi-valued modulation method, such as 16-QAM or 64-QAM, the addition synthesis diversity that can obtain the significant effect can be selected. Further, in a modulation method, such as BPSK or QPSK, the selection synthesis diversity can be selected. In the diversity receiving device according the aspect of the invention, a predetermined judgment criterion for determining a synthesis pattern of modulation signals is set to the selection synthesis diversity or the addition synthesis diversity so as to correspond to a modulation method of received signals. The control unit selects a synthesis pattern of modulation signals according to a modulation method of received signals detected from the output of a synthesizing unit, regardless of the reception intensity detection signal.
The diversity receiving device according to the aspect of the invention may further include a unit that delays a signal indicating a line quality determined on the basis of the intensity of a received signal by a processing time of each system in synchronization with symbol detection of the received signal, and a unit that selects the selection synthesis diversity or the addition synthesis diversity on the basis of the line quality. With this configuration, since the selection of synthesis pattern can be performed for each symbol, it is possible to reduce power consumption without degrading reception performance, even in a system, such as a high-speed mobile or the like. In the diversity receiving device according to the aspect of the invention, the AFC and synchronizing unit and the demodulating unit delay line quality signals of the respective systems output by the control unit by a processing time in synchronization with the symbol detection performed by the AFC and synchronizing unit and deliver the delayed line quality signals to the next stage. Further, when the line quality signal does not indicate good line quality, the AFC and synchronizing unit and the demodulating unit output a non-selection candidate signal, which sets the corresponding system to an unselected system, to the control unit. The control unit outputs a plurality of line quality signals indicating that line quality is good when the reception intensity detection signals are equal to or more than the first threshold value, and controls an operation timing of a clock supply unit according to the non-selection candidate signal. The synthesizing unit synthesizes the modulation signals of the system selected according to the synthesis pattern selection signal and the line quality signal output by the demodulating unit.
The diversity receiving device according to the aspect of the invention may further include a unit that selects at least one received signal from a plurality of systems on the basis of an instruction from the outside. Further, the diversity receiving device according to the aspect of the invention may further include a unit that selects the selection synthesis diversity or the addition synthesis diversity on the basis of an instruction from the outside.
According to the aspect of the invention of the invention, since the power supply to the systems other than the selected system is interrupted, it is possible to reduce overall power consumption without degrading reception performance.